We're going to turn, now, to a violent home invasion, that has sparked a federal investign. Fbi and dea agents have joined the search for clues in an attack that put a prominent new hampshire doctor and his wife in the hospital. And john schriffen is in bedford, new hampshire, with the latest. Reporter: The driveway to this home is blocked off because this is a very active crime scene. While police suggest they do have some leads. They say at this point, none are specific enough to be helpful. Crime scene units comb through this million-dollar mansion throughout the night, looking for any evidence of who could have brutally assaulted dr. Eduardo casada and his wife, and leaving them for dead. The homeowners were confronted by a person or persons of interest. Reporter: This morning, agents from the fbi and dea have joined the investigation. As dr. Casada, a respected anesthesiologist, clings to life at the hospital where he normally works. Police say the couple was viciously attacked saturday night, after an apparent home invasion. His wife, sonia, was able to escape, covered in blood. She knocked on a neighbor's door after the attack. That's where police found her, shortly after someone called 911. It could have potentially been a hostage situation. That was a consideration that was part of the plan. But the overarching concern was for the safety of the homeowner and the child. Reporter: When police stormed the house, they found t couple's 2-year-old child unharmed and no sign of intruders. Dr. Casada, however, was near death. The focus of this case was the couple. And maybe in particular, the doctor. And that they went there, with intention to, perhaps, steal something. But also, to harm the doctor. Reporter: Last year, dr. Casada was reportedly arrested at the house, after a domestic disturbance call. The charges were later dropped. And police won't say if the two incidents are related. Meantime, this morning, this normally quiet town is reeling. At this point, police will not say if t family was targeted or if anything was stolen. Only that they have a person of interest. But no one under arrest.

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